<!DOCTYPE html>
<html lang="zh-cn">
    <head>
        <meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
        <title>纯CSS实现内凹导航栏</title>
        <link href="https://at.alicdn.com/t/c/font_179247_uja3277echo.css" type="text/css" rel="stylesheet" />
    </head>
    <body>
        <dl class="nav">
            <dd class="on"><i class="iconfont icon-shouye1"></i><span>首页</span></dd>
            <dd><i class="iconfont icon-zixun"></i><span>资讯</span></dd>
            <dd><i class="iconfont icon-fabu"></i><span>发布</span></dd>
            <dd><i class="iconfont icon-xiaoxi"></i><span>消息</span></dd>
            <dd><i class="iconfont icon-wode"></i><span>我的</span></dd>
            <div class="indicator"></div>
            <!-- <dt class="indicator"></dt> -->
        </dl>
    </body>
    <style>
        *{
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}
body{
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    background-color: #333333;
}
.nav{
    width: 375px;
    height: 70px;
    padding: 0 15px;
    border-radius: 5px;
    background-color: #fff;
    position: relative;
    display: flex;
}
.nav dd{
    width: 70px;
    height: 70px;
    position: relative;
    list-style: none;
    cursor: pointer;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    z-index: 10;
}
.nav dd i{
    display: block;
    position: relative;
    height: 70px;
    line-height: 70px;
    text-align: center;
    font-size: 24px;
    transition: all 0.5s;
}
.nav dd span{
    position:absolute;
    font-size: 12px;
    letter-spacing: 2px;
    transition: all 0.5s;
    opacity: 0;
    transform: translateY(20px);
}
.nav dd.on i{
    transform: translateY(-35px);
    color: #ffffff;
}
.nav dd.on span{
    opacity: 1;
    transform: translateY(10px);
}
.indicator{
    position:absolute;
    top: -50%;
    width: 70px;
    height: 70px;
    background-color: #ff6a00;
    border-radius: 50%;
    transition: all 0.5s;
    border: 6px solid #333333;
}

.indicator::before{
    content: '';
    position: absolute;
    top: 50%;
    left: -23px;
    width: 21px;
    height: 21px;
    border-top-right-radius: 20px;
    box-shadow: 1px -10px 0 0 #333333;
}
.indicator::after{
    content: '';
    position: absolute;
    top: 50%;
    right: -23px;
    width: 21px;
    height: 21px;
    border-top-left-radius: 20px;
    box-shadow: -1px -10px 0 0 #333333;
}
dd:nth-child(1).on~.indicator{
            transform: translateX(calc(70px * 0));
        }
        dd:nth-child(2).on~.indicator{
            transform: translateX(calc(70px * 1));
        }
        dd:nth-child(3).on~.indicator{
            transform: translateX(calc(70px * 2));
        }
        dd:nth-child(4).on~.indicator{
            transform: translateX(calc(70px * 3));
        }
        dd:nth-child(5).on~.indicator{
            transform: translateX(calc(70px * 4));
        }

    </style>
    <script>
        const $dd = document.querySelectorAll('.nav dd');
        $dd.forEach((item,index)=>{
            item.addEventListener('click',function(){
                $dd.forEach((_dd,_index)=>{
                    _dd.classList.remove('on');
                    this.classList.add('on');
                })
            })
        })
        </script>
        
</html>
